blunsford

Hello everyone. My first post. I just bought a 1973 with the LS4 454 engine. It's a shame to have an engine that big with an anemic 275 hp. I want modify it to 500 streetable hp (including AC). I built and used to drag race a 1967 Camaro in the 1980's and I have a good small block background. My Rat motor knowledge is limited.

I'm looking for a good cylinder head recomendation that won't break the bank, a cam shaft and lifter combo, and an intake and carb that will allow the stock hood.

I'm even considering a paxton style blower - any comments??

Also, what headers do you recommend, porcelean or chrome or other????

Thanks.

74 vert

Welcome to the Forum. I lived in Indy before moving to TN in 2000. Many members choose Jet Hot coated headers. I went with Jet-hot Hookers with sidepipes. I also purchased STS baffles. Click on my movie which was shot by a forum member during a dyno in Knoxville.


[Modified by 74 vert, 10:06 PM 9/11/2003]


[Modified by 74 vert, 10:07 PM 9/11/2003]

Glensgages

If yer '75 iron heads aren't 'junk', I'd think 500 HP and a similar TQ # are possible WITH those heads. I'm guessing a carb/intake, matching camshaft, and good exhaust system, should get your C3 running like it 'should've' from St. Louis.
Might talk to Edelbrock about one of their 'packages'.....

WA 2 FST

Being a blower-junkie at heart, I also considered a centrifugal type blower for my 454. It is originally a 454 HO (425hp/500tq...but these are GROSS hp #s from GM) and had 8.75:1 CR. Seemed pretty good for a blower.

The problem is packaging. I can work on most car-related things, but I am not a great fabricator...and that's what it will take to make a centri-blower work. There is just not any real room under there to mount the blower on the front of the motor. A turbo setup would probably be easier to fab up.

If you do get adventuresome and do a centri-blower, forget the Paxton, unless you go with a top-of-the-line NOVI 2000 type blower. ATI or Vortech are better units.

Assuming your 454 is running well now, I would have to guess that since it was rated at 275hp, its probably ~220rwhp (chassis dyno).

You can easily pick up ~175-200rwhp with a good set of heads, cam, intake, headers, carb and maintain EXCELLENT street manners/driveability. You ARE definitely limited in your intake choices, however, if you stick with the stock hood.

If you went with something like a rectangle port head (people say they don't make as good of low-end as oval ports, but aftermarket heads are proving this to be incorrect... my AFRs are a perfect example), then I would run an LS6 low-rise intake. It is a dual plane intake, so its good for low-end and mid-range power, yet should give you enough flow on the top-end to satisfy your goal. I did a lot of research and the consensus was it would cost me ~20-30hp, so I bit the bullet and went with the L88-style hood and a hi-rise intake.

But my combo is very simple, very streetable, and makes power from off-idle to way up to 6400 which is as high as I've spun it on the dyno.

AFR 305 heads (CNC'd chambers, but stock ports)
Comp Cams 230/230, .578/.578, 110 LSA hydraulic roller cam
Edelbrock RPM Air-Gap intake
Holley 950 HP carb
Hooker side-mounted headers w/ JCL baffles

Pushed me from 334rwhp/384rwtq (which is ~100rwhp more than you have now, more than likely) to 434rwhp/450rwtq...idles at 800rpm, and no bucking/surging even at light throttle at low cruise rpms. With a low-rise intake, this combo is still a solid 400-410rwhp (~470hp flywheel) machine.

I would think it would take a lot of work to get your stock heads close to the AFRs, but if you are good at doing that stuff yourself (porting, polishing, valve job, CC the chambers, milling, etc), then that would be a great way to save some serious $$.

69 N.O.X. RATT

Since you would like to do it on a budget I would take the heads you have and get them worked on. THe AFR's are GREAT heads, but exspensive and you do not need them to get to 500 HP. $750.00 should get you a decent port lob and some 2.25 intakes. I know the heads you have are Ovals, but I do not know which ones, none the less I would ask the guy who does your heads (Assuming you have them done) if he can get the flow up to 275-300 cfm at .550 lift. Theoretically you need at least 250 cfm at max lift to make 500 HP

The only performance intake I know of that will fit under the stock hood is the Torker (Edelbrock) not the best intake in the world, but it will support 500 HP in a 454.

As for a cam (assuming a 4 spd and 3.55 gears or better) would be something in the neighbor hood of 235-240 at .050, .550 or more lift, on a 110-112 lSA. (if you have enough compression to support it) 9.5 to 1 or better, if not mill the heads or get new pistons For budget reasons I would go with a solid flat tappet, the Comp 294s might be worth looking at.

A lot of guys make the mistake of under camming these big motors (you know who I am talking about :lol: )

I would top it off with a 850 DP and be on my way.

The ceramic coated headers are great, I use Super Comps. For your motor combination I would go with 1 3/4 primarys


[Modified by 69 N.O.X. RATT, 6:04 AM 9/12/2003]

WA 2 FST

D'oh! <---- takes one in the crotch.

Thing is, we both know big cam/low compression will suck big time for street use, even if it picks up a tad of top-end HP over the smaller cam... it will not be worth it. Average HP across the desired rev-range is what is important. Granted, I guess 9.5:1 CR is enough to support a 240+^ duration hyd. roller cam. I know that now. Maybe I'll swap it someday and pick up a little top end.

But this guy's 73 BB is a low CR motor (probably lower than my 454 HO's 8.75:1 was stock).

Bob Turner

Blunsford,

Welcome to the forum!

I built a 454 for my '74 last year. I used an article out of a Chevy High Performance magazine (March 2000) as guidance to building it.

They claim 480hp/ 507lbs of torque with this combo:

9.0 to one compression
Comp cams XE274 (230/236 duration at .050, .553/.555" lift 110 LSA)
Stock heads (those 049 heads would be perfect )
Demon 850 with vac. sec.
Performer RPM intake

I added the following:

2.19"/1.88 valves
Mild Pocket porting
Harland Sharp roller rocker arms
9.3 to one compression
Sanderson shorty headers
Proform HEI distributor/Accel 300 wires

I am happy with the combo. However, I need to get rid of the 3.08's and get some 3.70's back there since the power range of the cam is HIGHER than stock. I am not taking advantage of this at this time. The 3.08's aren't doing it for me!!!!

I can fax you a copy of this buildup if you want.

Bob :cheers:

427Hotrod

Hey..Welcome to Our World!! You're going to have fun here!

You have a heck of a nice basis to start with. But as you noted there is a lot left on the table considering the size motor you have.

You gotta get some compression in it. Somehow. Reality on those things is they often aren't even 8.0 to 1. More like 7.75 or so! Real anemic.

Not sure how far you want to go, but you really need to get it up to at least 10.0 even with iron heads. 9.5 if you want to be real conservative, but the cams I like will prefer 10.0. That's going to take either new pistons, angle milled heads/and or block or new heads with smaller chambers.

About the only thing out there with chambers that small are the Edelbrock EFI oval ports- 100cc. They will get you in the ballpark without changing pistons.

Are you planning on rebuilding it all? If so it's easy...get some domed pistons. 11.0 compression closed chamber ones with your heads will net around 10.0-10.2 or so max. Or use smaller domes and then mill the heads.

You can easily make 500 hp with your current heads. It will take some die grinder work and preferably some larger valves. Assuming 049 castings are on it. There were a couple of funky versions right along that time that have weird chambers.

Cam choice is the next biggee. Something in the 240-250 @.050 solid lifter range will work fine with a 110-112 LSA. Get as close to .600 lift as you can. The heads will love it. I prefer solids and I have a few favorite cams that are very easy on parts and don't require frequent adjustment. Pulling that A/C compressor out of the way is a PITA. You could do it with a hyd flat tappet, but at whatever performance level you end up at, it will NOT be as smooth as the solid. If you cheek up for a hyd or solid street roller, you open up tons of possibilities.

The flat hood is going to be tough to. But you can do it with the LS-6 intake that was suggested.

Again lots of possibilities and we can bench race this thing to get it all dialed in. Give us more parameters that you want.

Headers...whatever you pick get them Jethot coated. I'd use the 2" ones with full length tubes, not shorty ones. 1 7/8" would be OK, but I'd use the 2".

Sounds like if you are willing to buy a blower, we are in the range of building a real nice motor with good parts.


JIM

69 N.O.X. RATT

Are you guys sure the LS-6 intake will fit under the stock hood ? If so I agree use it, maybe cut the divider out a little.

I agree with everything you said Jim, maybe 250 at .050 is a little steep but who am I to talk with my 255 and 262 at .050 :lol: I guess all all depends on your definition of streetable.

Do you think he would be better off with the bigger headers, didn't your 540 start making more power at above 5000 with the 2 1/8 or so over the 2" I would think he would want 1 7/8 max, you know better than me though.

He certainly needs more compression.

WA 2 FST

I just pulled off a low-rise LS6 intake that was installed with my 454 HO before I bought the car. Fit under the stock BB hood easily. I believe there are two LS6 intakes...this one is definitely a "pancake" type intake. The runners literally go down before going back up into the head ports. Of course, this is also for rect. port heads, and he has oval ports from what I can gather.

Certainly needs more CR if Jim is right and he's at 7.75-8.0:1 stock. I would hate for him to put a lot of money into those heads, put in a significantly bigger cam, and be running compression under 9.0-9.5:1 minimum, or the car will be slower than it is now.

BB wowbagger

My old motor put out 507 Hp and around 450 Ft/lbs of torque with this setup:
#781 HEADS WITH 2.19/1.88 Valves
10.5:1 hyperpistons
Erson Hydralic cam .570/.570 lift (i think)
Performer RPM intake
Holley 850 Dp
This was a very Streetable engine that pulled really nice :thumbs: :cheers:

GDaina

Don't be squeemish to run .600 + lift cams...Comp Cams 288R, .623 gross lift, 244 @.050, 110, lots of power and torgue in any RPM range, idles at 750-800, and pulls lots of vacuum...mine has 14 inches.

This is a solid roller.

Chuck Harmon

69 N.O.X.

You really hit a home run with your combination, over 600hp and nearly 600 pounds of torque. Curious, how streetable is it? Does it idle well below 1000 now? Do the head lights pop up in less than 30 seconds, and withinn 10 seconds of each other?

I am hoping that my economical choice of 246/254 @ 0.050" will make my dreams come true! To get GDaina's results would be too good to be true. :smash:

Chuck

BB wowbagger

Thats the cam i will be using in my new engine i`m building now. :thumbs: :cheers:

69 N.O.X. RATT

Chuck: I am very pleased with the new combination. It idles at 1200 rpms, but will lug around in 6th gear on the freeway at 1500 rpms. I am glad I went with the wider 112 LSA, it seems to help a lot.

I think you are going to be very pleased with your new cam, it will idle, respond, and pull better than the L-88 cam did. I think you will notice the throttle responce the most. With the shorter duration, high lift and 12 to 1 compression it will generate come good cylinder pressure low in the rpm range, hang on. I'll bet it starts to get after it pretty good before 3000 rpms.

Let us know how it goes.

mountainmotor

Gents he has a A/C car. Compression should stay 9.5 and with A/C I certainly would not want to be running a solid lifter cam although I'm about the biggest proponent of those cams here :smash:

I'd say port the stock heads using larger valves or not. Hydraulic cam single pattern about 225@ .050 on the intake 112 LCA " intake centerline on 108 or so" stock intake manifold with the junk in the way inside the plenum machined out of it like a Performer manifold and headers. headers,headers ;) Zero decked for the Rat Motor

Make about 450-475 and be done with it - reworked Q-Jet or Holley Spreadbore betting this car has 3.08's :)

69 N.O.X. RATT

Curtis, good point about the A/C I did not notice that, he would probably throw belts with a solid cam.

Ryan77

I know desktop dyno is not the bottom line in building motors, but I ran this combo anyway:
-AFR 305 heads
-dual plane manifold
-850cfm carb
-large tube headers with mufflers
-9.5:1 compression
-Comp Cams Magnum 270H, 224 duration @.050, 110 LSA, .510"/.510" lift. Comp Cams says this is a good for a daily driver, slightly noticeable idle, and works with a stock convertor. Mountainmotor knows his stuff so I tried to find a cam similar to what he recommended.

The motor peaked at 487hp@5500 and 500+ft/lbs@4000-4500 :cool:

With the 280H cam, the motor made 491@6000 and 495ft/lbs@4500.

I would also go up to the 3.55 or 3.73 gears, but I would try the motor first and see if you still want more gearing out back :cheers:


[Modified by Ryan77, 8:25 PM 9/15/2003]

WA 2 FST

Ryan, as you may have already realized this is VERY close to my combo... I have a bit larger cam which was recommended by AFR with their heads (230/230, .578" lift int/ex, 110LSA). Peak HP is at 5600rpm and peak TQ is at 4500rpm. Assuming 15% driveline loss through my 5-speed this = 511hp/529tq. I don't know when throwing belts with AC is a problem on these cars, since mine is not equipped with it. And while I am still making good power at 6400rpm, I shift below that for sure. :)

With 3.36s the car spins the tires into 3rd. I need 3.08s. :lol:

Tominator

:lurk:
I love reading this post and some day hope to be able to do one of these big engines.